This invention deals with novel salts of substituted nitrogen or sulfur containing siliconates which are effective stabilizers for aqueous silicates, silica sols and other silica containing water, such as boiler water, geothermal water, antifreeze and coolant solutions.
Aqueous silicates are known as metal corrosion inhibitors for aqueous systems. One of the major disadvantages of such silicates, however, has been the fact that they are unstable and after prolonged use at elevated temperatures they tend to gel and eventually precipitate out of solution. There have been many efforts, therefore, to stabilize silicates so that they could be more persistant in their corrosion inhibiting properties.
Arthur N. Pines et al. in U.S. Pat. Nos. 3,312,622 and 3,198,820 describe combinations of siliconate-silicate polymers as corrosion inhibitors. Although the patent does not specifically describe the stabilization of silicates, it is very obvious from the specification that the so-called "novel organosilicon polymer" does in fact contribute to the persistency of the corrosion inhibition of the siliconate-silicate polymers of that invention. The novelty, as pointed out therein, is the use of silyl carboxylate salts in conjunction with the silicates. Such materials are discussed as enhancing the corrosion inhibition of common antifreeze compositions and as overcoming disadvantages of other prior art corrosion inhibitors such as handling and dispensing of the antifreezes; selective corrosion inhibition of certain metals, poor shelf life, tendency to attack rubber hoses, excessive foaming in use and the causing of alcohols to decompose.
In later issued patents, U.S. Pat. Nos. 3,341,469 and 3,337,496, Pine et al. describe another system that was found useful for inhibiting corrosion in aqueous alcohol compositions. It consisted of a mixture of an alkyl silsesquioxane, a siloxane modified with a cyanoalkyl or carbinol group and, a silicate. There materials are stated as being "remarkably soluble in aqueous liquids". Further, the compositions are alleged to overcome many of the above mentioned disadvantages.
Another U.S. Pat. No. 3,948,964, issued Apr. 6, 1976, describes the stabilization of partially hydrolyzed silicic acid esters using stabilizers selected from the organic compounds such as cyclic ethers, ether alcohols, carboxylic acid esters and ketones. Such stabilized materials are described as binders for zinc dust pigments and the like.
In U.S. Pat. No. 3,960,576, issued June 1, 1976, there is disclosed the use of organic phosphonates in conjunction with alkaline oxide silicates as corrosion inhibitors for metal surfaces. It is stated therein that in addition to its corrosion inhibiting properties, the materials have the advantage of preventing the crystallization and deposition of dissolved solids which tend to precipitate on hot heat transfer surfaces.
Finally, there is a disclosure in a co-pending U.S. patent application Ser. No. 891,584, filed Mar. 30, 1978, now abandoned in the name of Edwin P. Plueddemann, showing the use of siliconates of silylalkyl phosphonates to stabilize aqueous silicates.
Thus, what has now been discovered is the use of certain sulfur or nitrogen containing siliconate salts to stabilize soluble silicates in order to overcome the problems associated with the prior art products.